Microelectronic capacitors are becoming increasingly important in microelectronic devices. For example, microelectronic capacitors are widely used in integrated circuit memory devices, such as dynamic random access memory (DRAM) devices. Moreover, as the integration density of memory devices continues to increase, memory devices having larger per-unit area capacitance are often needed to compensate for the reduced capacitor size. Thus, much research has been performed to obtain larger capacitance in submicron devices.
As is well known to those having skill in the art, a capacitor includes first and second spaced-apart conductive electrodes with a dielectric therebetween. The first conductive electrode is often referred to as a storage electrode and the second conductive electrode is often referred to as a plate electrode.
Efforts have been made to obtain larger capacitance in microelectronic capacitors by increasing the dielectric constant of the dielectric. Many materials have been investigated for their high dielectric constant. For example, tantalum pentoxide (Ta.sub.2 O.sub.5) has been widely used but has produced problems of unacceptably large leakage current in thin films thereof.
FIGS. 1A-1C are cross-sectional views illustrating a conventional microelectronic capacitor including a tantalum pentoxide dielectric during intermediate fabrication steps. As shown in FIG. 1C, a capacitor is formed on a semiconductor substrate 11 and is preferably formed on an interlayer insulation layer 13 on the semiconductor substrate 11. A contact hole 14 in the interlayer insulation layer 13 may be provided. Storage electrode 15 may extend through the contact hole 14 to contact a microelectronic device in the semiconductor substrate 11 (not shown). A nitride film 17 is formed on storage electrode 15 for purposes which will be described below. A dielectric film 19 comprising tantalum pentoxide is then formed on nitride layer 17. A plate electrode 20 is formed on dielectric film 19 to complete the capacitor.
Referring again to FIGS. 1A-1C, a method of fabricating a conventional integrated circuit capacitor will now be described. As shown in FIG. 1A, an insulation material is deposited on a semiconductor substrate 11 having a transistor or other active device (not shown) therein. Then, a contact hole 14 and an interlayer insulation layer 13 are formed, for example, by etching the insulation material to expose the face of the semiconductor substrate 11. For example, the source region of a transistor (not shown) may be exposed. A conductive material is then deposited on the interlayer insulation layer 13. The conductive material fills the contact hole 14. The conductive material is then etched to form the storage electrode 15 over the contact hole 14. The conductive material may include for example silicon, polysilicon, amorphous silicon, and/or other conventional conductive materials.
Referring now to FIG. 1B, a silicon nitride (Si.sub.3 N.sub.4) film 17, also referred to herein as a nitride film, is formed on the storage electrode 15. The nitride film 17 acts as an oxygen barrier. The nitride film 17 may be formed by nitrating the surface of the storage electrode 15 using ammonia. As is well known, the purpose of the nitride film 17 is to reduce, and preferably prevent, the growth of an oxide film between the storage electrode 15 and the dielectric film which is subsequently formed.
Referring now to FIG. 1C, a dielectric film 19 is formed. Dielectric film 19 is preferably tantalum pentoxide. The semiconductor substrate 11, including the dielectric film 19 is then thermally treated using dry oxygen (O.sub.2). The dry O.sub.2 treatment reduces or prevents leakage current from increasing due to oxygen vacancies in the dielectric film 19. The dry O.sub.2 treatment is preferably performed at 800.degree. C. for 30 minutes. A plate electrode 20 is then formed on tantalum pentoxide film 19 using conventional methods.
Unfortunately, it has been found that an ammonia (NH.sub.3) radical is produced on the surface of the nitride film 17 which may cause damage to the dielectric film 19 and thereby increase the leakage current. Moreover, since the thickness of the dielectric film 19 and the nitride film 17 generally determine the capacitance of the capacitor, the nitride film 17 should be thin. Accordingly, limitations on the thickness of the nitride film 17 may prevent the complete suppression of the growth of the oxide film between the storage electrode 15 and the dielectric film 19. This oxide film therefore increases the thickness of the dielectric film 19 and may reduce the overall capacitance of the capacitor.